This blood clotting problem is the most important treatable cause of recurrent miscarriage. It happens when your immune system makes abnormal antibodies that attack fats called phospholipids in your blood.
This makes the blood more ‘sticky’ and likely to clot, which is why APS is sometimes called ‘sticky blood syndrome’.
It is also known as ‘Hughes syndrome’ after the expert who named it. It is not clear why these antibodies cause miscarriage.
They may stop the pregnancy embedding properly in the uterus (womb); or they may interfere with blood flow to the placenta, which supports the baby.
APS can also lead to problems in later pregnancy, including the baby not growing enough, pre-eclampsia or stillbirth.
Other blood clotting problems
Some inherited blood clotting disorders can cause recurrent miscarriage, particularly after 14 weeks. These include:
Factor V Leiden
Factor II (prothrombin)
Gene mutation
Protein S deficiency
Abnormal chromosomes
The chromosomes in every cell of your body carry hereditary information in the form of genes.
Everyone has 23 pairs of chromosomes, and 22 of these are the same in men and women. The 23rd pair is different because they determine gender.
Men normally have one X and one Y chromosome and women two X chromosomes.
A baby inherits half its chromosomes from each parent.
About half of all miscarriages happen because the baby’s chromosomes are abnormal. This is not usually an inherited problem: it happens when the egg and sperm meet or soon after the egg is fertilised.
The older you are the more likely this is to happen. Much less commonly (in less than five in one hundred couples with recurrent miscarriage), one partner carries a chromosomal defect called a ‘balanced translocation’. This doesn’t cause a problem for the parent, but it can be passed on to the baby as an ‘unbalanced translocation’.
This means that some genetic information is duplicated and some is missing.
Cervical weakness
It is also known as ‘incompetent cervix’
Some women, probably less than one in a hundred, have a weakness in the cervix that allows it to dilate too early.
This is a known cause of late (second trimester) miscarriage.